Increase of capacity on the Shinkansen high- speed line using virtual coupling Tilo Schumann DLR Institute of Transportation Systems, Braunschweig, Germany Abstract The coupling and decoupling of trains while they are in motion is one of the research fields of the DLR project Next Generation Train. The coupling will be non-mechanical, but virtual and will be maintained by means of distance control technology. A special challenge of the virtual coupling in railway operation is the peril point of the switch in case of failure during the passage of two trains which are coming from different tracks, running in close succession at high- speed. Therefore some concepts are unrealizable with the current switch technology. Nevertheless there are situations where virtual coupling seems promising. One scenario is the virtual coupling at low speed, e.g. in the proximity of a station, where a safe brake is possible in case of a switch failure. The “Shinkansen” scenario aims to increase line capacity on the Tokaido high-speed line in Japan between Tokio and Osaka. The fastest “Nozomi” trains are stopping only at major stations. These stations have two tracks per direction with a 400 m platform. The idea is to double the number of Nozomi trains. So in every stopping station, there are two trains arriving and departing in a short interval. The distance on the open line is not that close, so it is more a ride within relative braking distance than a virtual coupling. To evaluate that scenario a special railway operation simulation has been developed, which is able to handle virtual coupling. The simulation shows the possibility to increase seating capacity from 15,000 to 23,000 seats per hour and direction. One bottleneck is occurring in Nagoya, where an additional platform is needed. Also the return time in Tokio has to be shortened to no more than 15 minutes. Keywords: Virtual Coupling, Next Generation Train, Shinkansen, Capacity Increase 1 Introduction Splitting and coupling of trains is currently done while stopping at stations. The idea to move this action to the line promises some benefits compared to the current situation. Today coupling and splitting enables a more intensive use of the network because two trains merge into one and therefore have less capacity requirements. This is because the track capacity is primarily restricted by the number of trains but not by the length of trains. In addition less operating staff is needed and the vehicle utilisation gets more efficient. Compared to a feeder line system train coupling provides a convenient travel for the passengers without the need to change trains. The only challenge for the passenger is to be in the right section before the train is split up. One handicap is the coupling procedure. Due to the mechanical character technical failures may occur and the synchronisation of trains is challenging in a system in case of delays. To cope with this, larger buffer times are planned, resulting in negative effects on the overall travel time. The present paper discusses operational scenarios using “virtual coupling”, which means that the coupling is not done mechanically anymore. The close distance between two trains, which could be e.g. 10 metres, is maintained with localisation and communication technology. The virtual coupling is part of the research project Next Generation Train (NGT) of the German Aerospace Center (DLR) [1]. Figure 1: Impression of the virtual coupling of two NGT Link trains 2 Virtual Coupling Operational Scenarios The switch is one very important constraint for the development of operational scenarios. This is due to the fact that the switching may fail and the next train has to be able to stop before passing the switch [2]. With this constraint the benefit of virtual coupling is limited. The following discussion distinguishes between two switch technologies: • Network with conventional switches • Network with passive switches at junctions Passive switches allow the trains to select their way themselves. There are no movable parts which could fail. Unfortunately there are no practical solutions for passive switches for high-speed traffic. 2.1 Scenarios with conventional switches 2.1.1 Slip Coaching The Slip Coaching Scenario has its origin in the 19th century in the United Kingdom [3]. At that time the carriages at the end of a train were uncoupled from the rest in order to stop at a station. The main part of the train continued the journey without loss of time. A disadvantage is the effort for shunting and the coupling to the opposite train. With electric multiple units this procedure becomes easier because there are no shunting locomotives necessary and also the coupling is possible. For this the slip train part has to accelerate ahead of the non-stopping part of the train. For safety reasons the accelerating train has to start early and travel a longer part alone, so that a virtual coupling manoeuvre can be done without violating the braking distance section in front of the non-stopping part. This scenario is not investigated deeper yet, but there are possible applications within the German ICE network. For example smaller cities like Göttingen, Kassel or Fulda are stations where the passenger volume is lower and the percentage of transients is very high. A slip procedure is likely to reduce travel time. 2.1.2 “Shinkansen” Scenario This is the scenario which this paper especially focusses on. It is named after the Japanese high-speed network, because this is an obvious application area for the procedure. The initial situation is a railway line which is heavily utilized by homogeneous traffic. There is the necessity for extra capacity especially on the section Tokio-Osaka, wherefore the Chuo-Shinkansen (with maglev technology) is planned. The idea is to increase the capacity with virtual coupling. To avoid the switch problem, the coupling happens close to the stopping stations where the speed is lower and therefore the braking distances are shorter. When the first train passed the common switch, the second train starts and enters the occupied block respectively follows the first train in a relative braking distance which also can be the virtual coupling (if both are running the same speed). Additionally the stopping time for the Kodama trains could be reduced, if two overtaking trains are virtual coupled (see Figure 2). Figure 2: Schematics of virtual coupling scenarios with conventional switch 2.2 Scenarios with passive switches 2.2.1 Coupling and splitting at junctions This is the “classic” scenario considering the virtual coupling. Two trains arrive from different lines and pass a switch at a junction within a short time interval. Then they are coupling virtually, continue their journey together. Later they split ahead of the dividing switch and continue their journey on different lines (see Figure 3). The challenges for this scenario are the creation of a switch which can be passed safely in any situation and state and the exact coordination of speed and position of the trains. A difficult case is a loss of speed of the designated first train shortly before passing the switch. This could result in a side-on-collision, so the speed of the second train has already to be regulated before the coupling procedure. Since there are no passive switches available for high-speed traffic this scenario is not further investigated here. 2.2.2 “Highway” Scenario The highway scenario is similar to the coupling-and-splitting-scenario, however the trains are not coupling virtually but following each other at least with the relative braking distance. They are not trying to reduce the distance in such a way that they reach the “coupled state”. This would lead to a longer travel time for the leading train because of lowering the speed. 2.2.3 “Freeway” Scenario The freeway scenario is the “most fictional” of all scenarios. The eponym is the road type freeway, where there are at least two lanes per direction. This is also the goal for the railway line, which has at least four tracks for both directions. There are connecting switches in regular distance to allow overtaking of slower trains or getting away from the fast lane to give the way for faster trains (see Figure 3). Basically this is already realized on some railway lines in the world with the conventional signalling technology, but with the use of passive switches, virtual coupling and travelling within a relative braking distance the benefits are becoming even more significant. This scenario is also not investigated further. Figure 3: Schematics with virtual coupling scenarios with a new type of switch 3 Simulation Tool „DFSimu“ To evaluate the scenarios it is not possible to test the procedures in reality, but they can be simulated first. Conventional simulation tools like OpenTrack [4], RailSys [5] or FBS [6] are not able to handle virtual coupling or trains runs at relative braking distance. Some can handle moving block, but this allows only running with an absolute braking distance. The tool DFSimu was created by DLR in order to simulate railway operations with virtual coupling or at least travelling within a relative braking distance. The tool is written in Python and consists of different modules for • data handling, • simulation and driving dynamics calculation, • conventional signalling, • coupling and splitting, • infrastructure management, • train type management, • timetable management, • train management, • protocolling and result plotting, • OpenStreetMap import. The traffic of the Tokaido Shinkansen with 515 km of line length, 66 trains with 15,700 train-kilometres and the time between 16:00 and 21:00 can be simulated on a conventional laptop within 45 seconds. Afterwards the results can be plotted using Matplotlib. This includes graphical timetables, trainrun profiles, energy consumption profiles, line profiles and station occupation charts.